ArrayCollection's addAll() method has incorrect behavior. Take the following code for example:
var test:ArrayCollection = new ArrayCollection();
In 4.6, this behaves as expected, and according to documentation, returning "1,2,3,4,5,6,7,8,9". In 4.10.0, it appears as though any calls to addAll() add the new items to the end of the original list, instead of the entire list, so you get the incorrect result "1,2,3,7,8,9,4,5,6".